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[ajr3773]

After some much needed advice from this forum in the last 24hours ive been able to establish that its my secondary air injection system that keeps blowing one of the rubber pipes, (O/S).

Problem i now have, is that today my mechanic fitted a high pressure silicone pipe to join the SAI pipes but on the way home my O/S CAT has collapsed. (Same side that SAI pipe burst)

Ive read several posts about the problem being related to the non return valve sticking open but ive also read that it can occur due to a blocked or failed CAT causing exhaust gases to return back to the SAI.

Problem i now have is, has the CAT collapsed because the pipe that was fitted is too strong to burst again resulting in the additional pressure being forced down the CAT causing the collapse or is it likely that the CAT was failing anyway causing the gases to return back into the SAI or is it the non return valve thats stuck open.

Obviously im now going to replace both CAT's even though only one has failed but id hate to replace them with the knowledge of knowing this could happen again.

Can anybody advise what the best course of action is?

If i just replace the CAT's will the problem with the SAI dissapear?

Or would it make sense just to block off the 2 rubber pipes on the SAI and remove the power to the SAI pump. If so is it best to just remove the fuse or relay or just disconnect the plug from the pump. Does anybody know what fuse it is?

Very confused because i don't know if the CAT failing has caused the SAI pipe to burst or if it i,s as a result of the non return valve sticking open or an accumilation of both.

[RobG]

Just unplug it under the pass. wing. Don`t get aftermarket cats they are shite. Whereabouts are you located as I`m selling both genuine s/h cats off a 3.0ltr complete with lambdas

[ajr3773]

Thanks for the advice. Would i still need to blank off the ends or would just unplugging it stop the gases circulating.

Im in Northumberland. How much are you wanting for them. Could you post?

[RobG]

Thanks for the advice. Would i still need to blank off the ends or would just unplugging it stop the gases circulating.
Im in Northumberland. How much are you wanting for them. Could you post?

Unsure. You can remove the system at your leisure. Waste of bloody time in any case. As for the cats, scrap I can get £60-70 each but they`re on here. Can find out courier charges if need be.
http://www.omegaowners.com/forum/YaBB.pl?num=1306873318

[geoffr70]

Yeah Rob's right that the aftermarket cats aren't that great, but if for whatever reason you don't take him up on his offer of his cats, I have two aftermarket cats here, both o/s and n/s complete with lambda sensors. They are used, but were on a car for a few weeks before the engine went bang and are so shiny and clean it's unreal!

[RobG]

If you don`t wanna mess around unplugging it, pull fuse #29b in relay box by battery
http://www.omegaowners.com/forum/YaBB.pl?num=1176542235

[ajr3773]

Thanks. So the Exhaust gasses im getting circulating around at the moment won't circulate if the pump is unplugged?

[RobG]

If the valve is knackered it would need to be replaced, easiest way...............block the pipes going into exhaust manifolds. You can then leave everything in situ or rip it out when it suits

[ajr3773]

You see i don't know if the valve is knackered or whether its back pressure due to the CAT failing.

From what you say it would appear that the SAI system is useless anyways, so id probably be better off just blanking off the pipes but just so im sure i can't just pull the fuse can i, just incase it is the valve thats knackered because if the valve is knackered and the SAI system is disabled of power the gasses are still going to circulate??

Can you just confirm and clarify please?

[ajr3773]

Yeah Rob's right that the aftermarket cats aren't that great, but if for whatever reason you don't take him up on his offer of his cats, I have two aftermarket cats here, both o/s and n/s complete with lambda sensors. They are used, but were on a car for a few weeks before the engine went bang and are so shiny and clean it's unreal!

How much do you want for them and can you arrange courier?

[Abiton]

The non-return valve must be letting exhaust gases back up the air pipes towards the pump, or you wouldn't be having any trouble.

If the valve was working as it should, the more pressure in the exhaust, the tighter it should shut. IMHO.

May be able to service it, dunno.  I'd imagine it's just got a bit coked up, so that it doesn't close fully.  Bit of oven cleaner might sort it out. Maybe.  Not sure how accessible they are on the V engines, nor whether they look the same as the 2.0 ones.  :-/

[Marks DTM Calib]

Lets get this clear, if you are blowing the small rubber pipes near the exhaust manifolds then you have a blocked cat or centre section, there are no non-return valves in this part of the system.

[Abiton]

Lets get this clear, if you are blowing the small rubber pipes near the exhaust manifolds then you have a blocked cat or centre section, there are no non-return valves in this part of the system.

Hmmm, my mistake, I assumed ( ) that, as on the 2.0, there'd be a non-return valve between hot exhaust-connected (metal) pipework and any rubber air pipes.  Seems odd/daft that there isn't. 

Carry on.